The present invention relates to a moisture resistant low melting point glass composition for a magnetic head and a magnetic head, and more particularly to a glass composition used for the formation of a gap in a magnetic head or for coupling and filling the components of a head, and to a magnetic head utilizing it.
A glass composition for a magnetic head is used for various purposes, such as the fabrication of a magnetic head by joining a plurality of core chips made of a magnetic material such as ferrite and ferromagnetic metals, the embedding of the core chips thus formed in a slider made of ceramic or the like, the formation of the gaps between the cores, and filling or reinforcing the gaps between the core chips and other components of the head.
It is known that glasses mainly composed of PbO which are welded at low temperatures are appropriate as this type of glass composition, and various glass compositions mainly composed of PbO have been developed. As examples of this type of glass compositions mainly composed of PbO, a glass composition containing 27% PbO, 53% SiO.sub.2, 4.5% B.sub.2 O.sub.3, 5% Na.sub.2 O, 0.5% K.sub.2 O, 5% Li.sub.2 O, and 5% ZnO in terms of mole ratio, and a glass composition containing 47% PbO, 23% SiO.sub.2, 17% B.sub.2 O.sub.3, 3% Na.sub.2 O, and 11% Al.sub.2 O.sub.3 in terms of mole ratio are known.
However, such conventional glass compositions have a problem that they are poor in environmental durability especially in moisture resistance and water resistance. This has resulted in shortcomings such as alteration on the glass surface leading to discoloration, and a step formed between the surface of the glass and the slider which decrease the yield of a slider production process. The reason is that, in a glass composition containing too much PbO, PbO is dissolved in the moisture that adheres on the surface of the glass. Glasses having other compositions have problems in that those having high moisture resistance melt at high temperatures and those melting at low temperatures have poor moisture resistance. Therefore, a glass composition which has good moisture resistance and melts at low temperatures, is needed.
Further, when a step is formed on the surface of a glass as described above, it significantly deteriorates the reliability of a magnetic head, especially a digital head, and actually leads to damages on a recording medium. In the case of a magnetic head having a small gap width, there is a possibility that conventional glass compositions will no longer be usable as gap-filling materials. Therefore, a novel glass composition is needed.